This invention relates to methods for benefitting polymeric materials. More particularly, this invention relates to methods for incorporating beneficial components, for example, ultraviolet (UV) light absorbing components into polymeric materials, for example, into silicone polymers, to provide effectively benefitted polymer materials useful, for example, as lenses.
The incident light entering the eye is composed of the entire spectrum of wavelengths including the ultraviolet, visible, and infrared. The cornea preferentially filters UV light in the range of about 300 nm to about 400 nm. Thus, in the eye with its natural lens in place relatively little radiation of wavelengths less than about 400 nm reaches the posterior intraocular structures, e.g., the vitreous humor and the retina.
In the aphakic individual, i.e., that individual who has had the natural crystalline lens removed, there is a loss in protection for the retina from UV light in the above-noted range. Thus, the use of UV absorbing contact or intraocular lenses is particularly important for the aphakic person. It is further believed that UV light screening spectacles or contact lenses may retard the development of a cataract in the natural lens.
Although low molecular weight, non-polymerizable UV light absorbing compounds of various types are relatively easy to compound into polymer formulations and are effective in blocking UV radiation when compounded into polymer formulations, their extractability in various media may limit their utility. This extractability problem has been remedied by the synthesis of polymerizable, UV light absorbing monomers which conventionally are combined prior to polymerization with the other polymerizable monomers. This monomer blend is then subjected to polymerization conditions effective to form the polymer product. These covalently bonded UV light absorbing constituents are not extractable and do not phase separate from the remainder of the polymer.
Examples of polymerizable UV light absorbing components which may be incorporated into monomer blends prior to polymerization include the vinylsilylalkoxy arylbenzotriazole monomers disclosed in Dunks et al U.S. Pat. No. 4,803,254; the benzotriazole derivatives disclosed in Reich et al U.S. Pat. No. 4,868,251, Yoshida et al U.S. Pat. No. 4,380,643, Beard et al U.S. Pat. No. 4,528,311 and Besecke et al U.S. Pat. No. 4,612,358; and the benzophenone derivatives disclosed in Loshaek U.S. Pat. No. RE. 33,477 and Reich et al U.S. Pat. No. 4,868,251. The disclosure of each of these patents is incorporated in its entirety by reference herein.
One problem with the conventional methods of forming a polymer from a monomer mix including a polymerizable UV light absorbing monomer is that the UV light absorbing monomer may have an adverse effect or impact on the polymerization reaction, or on the other properties of the final polymer. Also, it may be somewhat difficult to combine the desired amount of UV light absorbing monomer with the remainder of the monomers prior to polymerization in order to achieve the desired UV light absorbing properties.
Clearly, it would be advantageous to provide new methods for incorporating UV light absorbing components, and other beneficial components, into polymer materials.